Ten-petal Sunflower, a native species, has been added to the USWildflowers database (09/23/2011.) Scientific name is Helianthus decapetalus. Photo below was taken in Grundy County, TN on September 17, 2011.   Go to the Ten-petal Sunflower detail page for more photos and information.

Thinleaf Sunflower, Ten-petal Sunflower, Forest Sunflower, Pale Sunflower – Helianthus decapetalus